A common method of moving downhole sleeves from an opened to closed position, or vice versa, is to use a shifting tool that is attached to the bottom of a work string. The more complicated shifting tools are hydraulically actuated. In those type tools, the latching mechanism is kept in a retracted position until shifting tool has reached the sleeve. The latching mechanism is then expanded, typically by fluid flow down the work string. Other shifting tools consist of a pair of spring-loaded opposing keys. The keys have a profile designed to seek out a mating internal profile on the sleeve. These tools are capable of passing other internal profiles in the tubing, but may be prone to fouling should debris work its way beneath the keys to obstruct their inward movement. A simpler shifting tool, that may be less likely to foul in debris-laden fluids, consists of a collet (similar shape as a bow-spring centralizer) with a profile also designed to engage a mating profile in the sleeve. For all of these shifting tool designs, translation of the work string while the shifting tool is engaged with the sleeve provides the opening or closing stroke for the sleeve. The present invention is intended for use on collet-style shifting tools. A collet is well-suited for snapping into the sleeve prior to actuation and snapping out of the sleeve after actuation due to its ability to deflect in a radial direction. In fact, the collet can be designed to successfully pass through other downhole devices with smaller inside diameters than the sleeve profile. However, a problem can occur when the shifting tool collet is asked to pass through a downhole device where the smaller bore is a sealing bore. The deflected collet fingers ride along the inside diameter of the sealing bore from end to end as the shifting tool passes through. Depending on the geometry of the collet fingers, the material types and hardnesses of the collet and seal bore, and the radial force required to deflect the fingers, the fingers can scratch or gall the seal bore impairing its ability to seal. Since the collet fingers' outside diameter is larger than the seal bore through which it is passing, each deflected finger will “ride” on its two outermost edges. Previous efforts to reduce the likelihood of damage included hand-grinding or machining a large radius on those outer edges. Those efforts have met with mixed success. Hand-ground edge breaks are inconsistent and can still leave points or ridges. Collets are typically made of heat-treated alloy to withstand the repetitive bending stresses they encounter, and even well rounded edges on a hardened steel collet finger could initiate galling when passing through seal bores of lower hardness material (e.g., 13 chrome 80K MYS). Another approach for reducing damage has been to coat the collet finger surfaces. However, since the shifting tool is a rental tool that is reused from well to well, the coating on the collet would have to be reapplied on a frequent basis as it wears during service. A third approach is to add a replacement insert of a softer material that would provide temporary protection and could be easily replaced such as a brass insert held in place by an angled groove shoulder and set screw. The downside of this particular application of that concept is that it requires wider slots between collet fingers in order to install the inserts. Consequently, contact between the collet finger and sleeve profile as well as collet finger tensile area are significantly reduced.
U.S. Pat. No. 8,678,096 shows a bow spring centralizer with particulate material on the outer surface of the bow springs to resist erosion. U.S. Pat. No. 5,678,633 shows a hydraulic shifting tool; U.S. Pat. No. 3,051,243 shows a key type shifting tool; U.S. Pat. No. 7,993,085 shows a fastener used to push out a collet for fixation purposes.
What is needed and provided by the present invention in one of its forms is a way to protect the seal bores through which the collets have to pass in a compressed state before reaching the tool that they ultimately engage for operation thereof. A sacrificial softer material is disposed to contact the seal bore wall so that if there is to be any wear, the sacrificial material wears down. The material can be removably mounted to the collet so that it can be easily replaced when the tool is removed from the borehole. Various attachment methods are contemplated as well as devices to adjust the degree of protrusion of the sacrificial material.
The sacrificial material needs to be inserted in a way that it is retained for functionality without limiting the number of fingers just to accommodate the insertion or fixation technique. For example, FIG. 19 displays a laterally inserted sacrificial member 100 into an end of a dovetailed groove 102. The issue with this design is that it limits the device to having four fingers so that the members 100 can be inserted and retained with a set screw 104. Fewer fingers means higher stresses on each finger as dimensional transitions have to be negotiated and a more limited grip on the subterranean tool such as a sliding sleeve that ultimately has to be operated.
Those skilled in the art will better understand the variations of the present invention from a review of the detailed description with the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims.